Percutaneous transluminal coronary angioplasty (PTCA) is used to increase the lumen diameter of a coronary artery partially or totally obstructed by a build-up of cholesterol fats or atherosclerotic plaque. Typically a first guide wire of about 0.038 inches in diameter is steered through the vascular system to the site of therapy. A guiding catheter, for example, can then be advanced over the first guide wire to a point just proximal of the stenosis. The first guide wire is then removed. A balloon catheter on a smaller 0.014 inch diameter second guide wire is advanced within the guiding catheter to a point just proximal of the stenosis. The second guide wire is advanced into the stenosis, followed by the balloon on the distal end of the catheter. The balloon is inflated causing the site of the stenosis to widen. The dilatation of the occlusion, however, can form flaps, fissures and dissections which threaten reclosure of the dilated vessel or even perforations in the vessel wall.
Although the dimensions in the above example are suited to the coronary arteries, any body lumen can be treated by percutaneous transluminal angioplasty (PTA), including the vas deferens, ducts of the gallbladder, prostate gland, trachea, bronchus and liver. The body lumens range in diameter from small coronary vessels of 3 mm or less to 28 mm in the aortic vessel. The invention applies to acute and chronic closure or reclosure of body lumens.
It is advantageous for a catheter to have visible marker bands on the catheter shaft that can be viewed using a fluoroscope machine to position the catheter in relation to the lesions. It is also advantageous for a catheter shaft to have a smooth outer surface with minimal bumps from the marker bands. What is needed is marker bands which can be visible using a fluoroscope and also which do not create a significant increase in diameter so that the catheter can slide easily through the lesion.
U.S. Pat. Nos. 5,489,277 and 5,256,158 to Tolkoff et al. for "Device Having a Radiopaque Marker for Endoscopic Accessories and Method of Making Same" discloses a radiopaque ring that is inserted into an expanded section of tubing, followed by the relaxation of the tube to its original dimensions. U.S. Pat. No. 5,485,667 to Kleshinski for "Method for Attaching a Marker to a Medical Instrument" discloses a marker made of tubular radiopaque shape memory material that is deformed and then slid over or into the tubing and then heated so that the shape memory material returns to its original shape and attaches to the tubing.